ATHENS: EU powerhouse Germany told Turkey and Greece on Tuesday to defuse their escalating row over gas exploration in the Mediterranean or risk sparking a "catastrophe".

German Foreign Minister Heiko Maas issued the warning after meeting Prime Minister Kyriakos Mitsotakis and other Greek officials in Athens on the first leg of a mission to try to end the standoff.

The discovery of major gas deposits in waters surrounding Cyprus and the Greek island of Crete has triggered a scramble for energy riches and revived old regional rivalries.

"The spiral of escalation (between the two neighbours) is raising major worries," Maas said before he travels to Turkey later Tuesday.

"The least spark can lead to catastrophe," said Maas, whose country currently holds the rotating six-month European Union presidency.

"We absolutely and immediately need signals for de-escalation and a will for dialogue."

The German mediation effort comes just as Greece and Turkey, traditionally uneasy allies in the NATO military grouping, are set to hold rival war games near Crete in the eastern Mediterranean Sea.

Maas called for an end to "all destructive and provocative activities" in the eastern Mediterranean.

Turkey and Greece have often been at odds and almost went to war over some uninhabited islets in the Aegean Sea in 1996.

Fellow EU heavyweight France has taken a tougher line against Ankara, sending warships to help Greece in the standoff.

Turkey is not only a longstanding ally within NATO, which includes many EU countries, but is party to a deal with Brussels to prevent uncontrolled migration to Europe, which dramatically split the bloc in 2015.

Last week, EU foreign ministers convened an emergency video conference after Greek and Turkish warships collided in hotly disputed circumstances.